Re: Proposed new text for noaccess

On 29 October 2013 11:04, Martin Thomson <martin.thomson@gmail.com> wrote:
>> Can you write up a complete
>> use case where you will want to use the "noaccess" constraint

Another use case: "Pre-negotiate Session"

A user browses an unfamiliar site where they require assistance from a
support agent.  They are prompted to accept a real-time session with
the support agent.  The user accepts the call and then provides
(temporary) consent for access to their camera and microphone.  The
user expects to be able to speak immediately upon granting consent.

In order to ensure that the session is effectively live prior to
consent being granted, session negotiation must have completed.  The
application is able to use a stream marked with a "noaccess"
constraint to build a session, thereby ensuring that the session is
live when the user grants their consent to access live media.

This comes with some fingerprinting risks, but I believe those can be
mitigated.  The substance of the risk is that different sources
produce different negotiation points, allowing a site to glean
additional information about the source.  For instance, native camera
resolution might be leaked.  This can be mitigated by having browsers
report a fixed resolution (or a small set of options) for the purposes
of negotiation based on noaccess streams.  The different encoding
profiles (codec + sundry) might also require some massaging to avoid
excessive leaks, though non-software encoder configurations will
inevitably leak a little.

The alternative is to force applications to acquire consent for a
media source prior to commencing negotiation.  That's going to result
in problems like the clipped "hello", which I would rather avoid.

There are also other ways to achieve this sort of outcome, but each of
those come with varying risks of the negotiation failing to negotiate
properly.  This has the advantage of negotiating with browser having
full knowledge of the actual source, just not the image or sounds.

Received on Tuesday, 29 October 2013 18:20:27 UTC